Measurement device and measurement method

Abstract

A measurement device includes a light sensing element on which light from a measurement target region placing a measurement target thereon forms an image, and a plurality of light emitting elements that are disposed around the light sensing element and radiate light to the measurement target region, wherein the plurality of light emitting elements are disposed to be tilted with respect to the normal line of the measurement target region such that the central line of radiated emission from each of the light emitting elements passes through a substantial center of the measurement target region.

The application is claimed as follows: 
     
       1. A measurement device comprising:
 a light sensing element on which light from a measurement target region placing a measurement target thereon forms an image; and 
 a plurality of light emitting elements that are disposed around the light sensing element in a ring shape and radiate light to the measurement target region, 
 wherein the plurality of light emitting elements are disposed to be tilted with respect to the normal line of the measurement target region such that the central line of radiated emission from each of the light emitting elements passes through a substantial center of the measurement target region, 
 wherein an angle formed by the central line of the radiated emission and the normal line of the measurement target region is set according to a separation distance between the measurement target region and the light sensing element. 
 
     
     
       2. The measurement device according to  claim 1 , wherein if the separation distance is equal to or less than a predetermined threshold value, the angle is set to 45°, and if the separation distance exceeds the predetermined threshold value, the angle is set to be less than 45°. 
     
     
       3. The measurement device according to  claim 1 , wherein the measurement target region is provided to face the light sensing element. 
     
     
       4. The measurement device according to  claim 1 , wherein 4N (where N is an integer equal to or more than 1) light emitting elements are disposed around the light sensing element at an interval of (90/N)°. 
     
     
       5. The measurement device according to  claim 4 , wherein the light emitting elements which radiate light having different N wavelengths are disposed by four for each wavelength as the plurality of light emitting elements. 
     
     
       6. The measurement device according to  claim 5 , wherein twenty light emitting elements which radiate light having different 5 wavelengths are disposed around the light sensing element at an interval of 18°. 
     
     
       7. The measurement device according to  claim 6 , wherein the light having the different 5 wavelengths has 500 nm, 540 nm, 580 nm, 620 nm, and 660 nm, respectively, as a central wavelength. 
     
     
       8. The measurement device according to  claim 7 , wherein the full width at half maximum of the light having 580 nm as the central wavelength is smaller than the full width at half maximum of the light having 500 nm, 540 nm, 620 nm, and 660 nm as the central wavelength. 
     
     
       9. The measurement device according to  claim 5 , wherein the light emitting elements which radiate the light having the different N wavelengths radiate the light in a time divisional manner so as to have a predetermined pulse width using N pulses. 
     
     
       10. The measurement device according to  claim 5 , wherein each light emitting element radiates a light of different wavelength from adjacent light emitting elements. 
     
     
       11. The measurement device according to  claim 1 , wherein a numerical aperture of the radiated emission which is provided to the measurement target region is equal to or less than 0.2. 
     
     
       12. The measurement device according to  claim 1 , wherein the plurality of light emitting elements radiate light having the same wavelength characteristic. 
     
     
       13. The measurement device according to  claim 12 , wherein the plurality of light emitting elements respectively and simultaneously radiate white light so as to have a predetermined pulse width. 
     
     
       14. The measurement device according to  claim 12 , wherein a light sensing surface of the light sensing element is divided into N regions, and
 wherein an optical filter which transmits light having different N wavelengths therethrough is provided at an upper side of each of the regions. 
 
     
     
       15. The measurement device according to  claim 14 , wherein the light sensing surface of the light sensing element is divided into five regions, and
 wherein the optical filters transmit light having 500 nm, 540 nm, 580 nm, 620 nm, and 660 nm as a central wavelength therethrough. 
 
     
     
       16. The measurement device according to  claim 15 , wherein the full width at half maximum of the light having 580 nm as the central wavelength is smaller than the full width at half maximum of the light having 500 nm, 540 nm, 620 nm, and 660 nm as the central wavelength. 
     
     
       17. The measurement device according to  claim 15 , wherein collimated diffuse reflection from the measurement target region is incident to the optical filters. 
     
     
       18. The measurement device according to  claim 1 , wherein the size of the measurement target region is substantially the same as the size of a spot formed by light radiated from the plurality of light emitting elements. 
     
     
       19. The measurement device according to  claim 1 , wherein the measurement device is disposed inside a casing at which an opening portion is provided, and
 wherein the measurement target region is a human skin surface placed on the opening portion. 
 
     
     
       20. The measurement device according to  claim 1 , wherein light sensed by the light sensing element is used to generate measurement information including at least one of information for a skin reflection spectrum and reflectance at a specific wavelength. 
     
     
       21. The measurement device according to  claim 1 , wherein said angle is substantially the same for each of the plurality of the light emitting elements. 
     
     
       22. A measurement method comprising:
 radiating light of a predetermined wavelength from a plurality of light emitting elements which are disposed around a light sensing element in a ring shape on which light from a measurement target region placing a measurement target thereon forms an image, and which radiate light to the measurement target region, such that the central line of radiated emission from each of the light emitting elements passes through a substantial center of the measurement target region, wherein an angle formed by the central line of the radiated emission and the normal line of the measurement target region is set according to a separation distance between the measurement target region and the light sensing element; and 
 causing the light sensing element to sense diffuse reflection light from the measurement target region.